Impeller

ABSTRACT

An impeller includes a plurality of portions, a plurality of bends, and a plurality of blades. A substantial thickness of a portion is smaller than a substantial thickness of another portion more adjacent to a central axis of the impeller. Each bend is interconnected between two portions adjacent to each other. The blades are formed on the portion most distant to the central axis. The overall weight of the impeller is reduced. Furthermore, the impeller has improved mass uniformity and hence improved overall balancing precision.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an impeller and, more particularly, the present invention relates to an impeller including a plurality of portions formed by injection molding in which a substantial thickness of a portion is smaller than a substantial thickness of another portion more adjacent to a central axis of the impeller to improve the balancing precision of the impeller.

2. Description of Related Art

The temperature results from operation of electronic devices becomes higher and higher while the effects of the electronic devices are enhanced. An excessively high temperature environment adversely affects the effects and stability of the electronic devices. Heat-dissipating units have, therefore, become one of the necessities of current electronic devices. Heat-dissipating devices generally include heat-dissipating fans having sizes matching with the volumes of the electronic elements in the electronic devices. To reduce the total weight of the heat-dissipating fans, the impellers are generally made of injection molded plastic

For a current impeller formed by injection molding, most portions of the impeller including a hub, an annular plate, and impellers, etc. have substantially an identical substantial thickness in an attempt to maintain balancing precision and overall structural strength. During injection molding, molten plastic material is filled by an injection nozzle into a mold cavity of a mold via an inlet port of the mold. To reduce resistance during injection of the injection nozzle, an axial thickness of the mold cavity aligned with the inlet port must be at least 0.3 mm. Furthermore, a back pressure is generated while the molten plastic material enters the space in the inlet port. The more the plastic molten material is filled, the larger the back pressure is. Thus, it is difficult to fill the molten plastic material into the mold cavity in a uniform manner, particularly in the areas distant to the inlet port. As a result, the mass uniformity of the portions of the impeller such as the annular plate or the blades distant to the central axis of the impeller is poor. Particularly, non-uniform distribution of the molten plastic material in the mold cavity tends to occur in the areas behind the bends in the mold cavity. As a result, required mass uniformity throughout various portions of the impeller can not be obtained, leading to reduced overall balancing precision.

It is, therefore, a need for an improved impeller that has required mass uniformity and improved balancing precision.

OBJECTS OF THE INVENTION

An object of the present invention is to provide a novel impeller that has required mass uniformity.

Another object of the present invention is to provide a novel impeller that has improved balancing precision.

A further object of the present invention is to provide a novel impeller that can easily be manufactured.

SUMMARY OF THE INVENTION

An impeller according to the preferred teachings of the present invention includes a shaft base defining a central axis about which the impeller rotates. A top portion is connected to the shaft base, and an annular wall portion has an end connected to an end of the top portion. A first bend is interconnected between the annular wall portion and the top portion. The annular wall portion has a substantial thickness smaller than that of the top portion. An annular plate portion is connected to the other end of the annular wall portion. A second bend is interconnected between the annular wall portion and the annular plate portion. The annular plate portion has a substantial thickness smaller than that of the annular wall portion. A plurality of blades are formed on an outer periphery of the annular plate portion.

The impeller having such a structure can be formed at a smaller injection pressure to avoid deformation of the product. The smaller injection pressure maintains the quality stability of the products while avoiding the waste of materials. Even the areas in the mold cavity distant to the inlet port can be uniformly filled at the smaller injection pressure. The overall weight of the impeller is reduced. Furthermore, the impeller has improved mass uniformity and hence improved overall balancing precision.

Other objects, advantages and novel features of this invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded perspective view of an impeller of a first embodiment according to the preferred teachings of the present invention.

FIG. 2 shows a cross sectional view of the impeller of FIG. 1.

FIG. 3 shows a perspective view of an impeller of a second embodiment according to the preferred teachings of the present invention.

FIG. 4 shows a cross sectional view of the impeller of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An impeller 1 of a first embodiment according to the preferred teachings of the present invention is shown in FIGS. 1-2. The impeller 1 includes a shaft base 10 defining a central axis about which the impeller 1 rotates. The impeller 1 further includes a plurality of portions and a plurality of bends. In the first embodiment shown, according to the distance to the shaft base 10, the plurality of portions correspond to a top portion 11 of a hub of the impeller 1 (i.e., the first portion), an annular wall 12 of the hub of the impeller 1 (i.e., the second portion), and an annular plate portion 13 (i.e., the third portion). Specifically, the top portion 11 of the hub extends radially outward from a circumference of the shaft base 10. The annular wall portion 12 of the hub extends from an outer circumference of the top portion 11 of the hub in a direction perpendicular to a general plane on which the top portion 11 lies. The top portion 11 and the annular wall portion 12 together define an inner space “a”. The annular plate portion 13 extends radially outward from an end of the annular wall portion 12. The impeller 1 further includes a plurality of blades 14 extending radially outward from the annular wall portion 13 and spaced at regular intervals. The top portion 11 has a substantial thickness T1 larger than that T2 of the annular wall portion 12, whereas the substantial thickness T2 of the annular wall portion 12 is larger than that T3 of the annular plate portion 13. The substantial thickness T4 of each blade 14 is substantially the same as that T3 of the annular portion 13 in the first embodiment.

In the first embodiment shown, the impeller 1 includes at least first and second bends 15 and 16. The first bend 15 is formed and interconnected between the top portion 11 and the annular wall portion 12. The first bend 15 has an angle θ₁ in a range between 90° and 110° (namely, the angle between the top portion 11 and the annular wall portion 12). The second bend 16 is formed and interconnected between the annular wall portion 12 and the annular plate portion 13. The second bend 16 has an angle θ₂ in a range between 30° and 150° (namely, the angle between the annular wall portion 12 and the annular plate portion 13).

The impeller 1 is integrally formed by injection molding of a plastic material such as polyphenylene sulfide, polypropylene, resin, or polyester ester ketone that has better flowability in its molten state. Molten plastic material is filled by an injection nozzle through an inlet port of a mold for the impeller 1 into a mold cavity of the mold to form the hub, the annular plate 13, and the blades 14 of the impeller 1. The inlet port is generally located in a position of the mold corresponding to the central axis of the impeller to allow uniform filling of plastic material into the mold cavity. The mold cavity has a shape and size corresponding to that of the portions and the bends of the impeller 1 to be formed.

During injection, the injection nozzle provides an appropriate injection pressure for conveying and filling molten plastic material into the mold cavity. In the mold of the impeller 1 of the first embodiment according to the preferred teaching of the present invention, the thickness of a portion of the mold cavity (corresponding to, for example, the annular wall portion 12 of the impeller 1) of after a bend (corresponding to, for example, the first bend 15) is smaller than that of another portion of the mold cavity (corresponding to, for example, the top portion 11 of the impeller 1). This allows the impeller 1 to be formed at a smaller injection pressure to avoid deformation of the product. It is noted that a larger injection pressure in conventional injection molding processes is required for forcing the molten plastic material to fill areas in the mold cavity distant to the inlet port; yet excessive pressure will cause deformation of the product and a waste in material. In an impeller 1 formed in such a mold cavity, the substantial thickness of a portion of the impeller 1 is smaller than that of another portion of the impeller 1 more adjacent to the central axis of the impeller to improve the balancing precision of the impeller (T3<T2<T1). The amount of material utilized is saved, and the total weight of the impeller 1 and the manufacturing costs thereof are reduced. The smaller injection pressure maintains the quality stability of the products while avoiding the waste of materials. Even the areas in the mold cavity distant to the inlet port can be uniformly filled at the smaller injection pressure. Each portion of the resultant impeller product has improved thickness uniformity and improved mass uniformity. The overall balancing precision of the impeller 1 is enhanced, and the period of time of subsequent procedures for adjusting the balancing properties of the impeller 1 is shortened.

FIGS. 3 and 4 show an impeller 1 of a second embodiment according to the preferred teachings of the present invention. Compared to the first embodiment, the plurality of blades 14 extend upward in an axial direction from a side of the annular wall portion 13. The blades 14 are arc-shaped and annularly arranged on the annular wall portion 13 at regular intervals. The substantial thickness T1 of the top portion 11 of the impeller 1 decreases radially away from the shaft base 10. Nevertheless, the minimum thickness of the top portion 11 is still larger than the substantial thickness T2 of the annular wall portion 12 to enhance the structural strength of the top portion 11 while providing enhanced thickness uniformity and mass uniformity in the other portions of the impeller 1 after formation.

The disadvantages of the conventional injection molding processes for forming impellers are avoided by the impellers 1 according to the preferred teachings of the present invention including a plurality of portions in which the substantial thickness of a portion is smaller than the substantial thickness of another portion more adjacent to a central axis of the impeller to improve balancing precision of the impeller. The impellers 1 according to the preferred teachings of the present invention have light weights, enhanced mass uniformity, and enhanced balancing performance.

While the principles of this invention have been disclosed in connection with specific embodiments, it should be understood by those skilled in the art that these descriptions are not intended to limit the scope of the invention, and that any modification and variation without departing the spirit of the invention is intended to be covered by the scope of this invention defined only by the appended claims. 

1. An impeller comprising: a shaft base defining a central axis about which the impeller rotates; a top portion connected to the shaft base; an annular wall portion having an end connected to an end of the top portion, with a first bend being interconnected between the annular wall portion and the top portion, and with the annular wall portion having a substantial thickness smaller than that of the top portion; an annular plate portion connected to another end of the annular wall portion, with a second bend being interconnected between the annular wall portion and the annular plate portion, and with the annular plate portion having a substantial thickness smaller than that of the annular wall portion; and a plurality of blades formed on an outer periphery of the annular plate portion.
 2. The impeller as claimed in claim 1, with the first bend having an angle in a range between 90° and 110°.
 3. The impeller as claimed in claim 1, with the second bend having an angle in a range between 30° and 150°.
 4. The impeller as claimed in claim 1, with the plurality of blades being annularly arranged on the outer periphery of the annular plate portion at regular intervals, and with each of the plurality of blades having a substantial thickness not larger than that of the annular plate portion.
 5. The impeller as claimed in claim 2, with the plurality of blades being annularly arranged on the outer periphery of the annular plate portion at regular intervals, and with each of the plurality of blades having a substantial thickness not larger than that of the annular plate portion.
 6. The impeller as claimed in claim 3, with the plurality of blades being annularly arranged on the outer periphery of the annular plate portion at regular intervals, and with each of the plurality of blades having a substantial thickness not larger than that of the annular plate portion.
 7. The impeller as claimed in claim 1, with the substantial thickness of the top portion of the impeller decreasing radially away from the central axis.
 8. The impeller as claimed in claim 2, with the substantial thickness of the top portion of the impeller decreasing radially away from the central axis.
 9. The impeller as claimed in claim 3, with the substantial thickness of the top portion of the impeller decreasing radially away from the central axis.
 10. An impeller comprising: a plurality of portions, with one of the plurality of portions most adjacent to a central axis about which the impeller rotates having a substantial thickness larger than that of remaining portions of the impeller, and with a substantial thickness of one of the remaining portions being smaller than a substantial thickness of another portion more adjacent to the central axis; a plurality of bends, with each of the plurality of bends being interconnected between two of the plurality of portions adjacent to each other; and a plurality of blades formed on an outer periphery of one of the plurality of portions that is most distant to the central axis.
 11. The impeller as claimed in claim 10, with the plurality of portions including at least a first portion and a second portion, with the first portion being a top portion of a hub of the impeller, with the second portion being connected to an end of the first portion, with the second portion being an annular wall portion of the hub of the impeller, and with a first of the plurality of bends being interconnected between the first and second portions.
 12. The impeller as claimed in claim 11, with the plurality of portions further including a third portion connected to an end of the second portion, with the third portion being an annular plate portion of the impeller, and with a second of the plurality of bends being interconnected between the second and third portions.
 13. The impeller as claimed in claim 12, with the plurality of blades being annularly arranged on an outer periphery of the third portion at regular intervals.
 14. The impeller as claimed in claim 12, with the first portion having a substantial thickness larger than that of the second portion, with the second portion having a substantial thickness larger than that of the third portion, and with each of the plurality of blades having a substantial thickness not larger than that of the third portion.
 15. The impeller as claimed in claim 13, with the first portion having a substantial thickness larger than that of the second portion, with the second portion having a substantial thickness larger than that of the third portion, and with each of the plurality of blades having a substantial thickness not larger than that of the third portion.
 16. The impeller as claimed in claim 10, with the substantial thickness of the top portion of the impeller decreasing radially away from the central axis.
 17. The impeller as claimed in claim 10, with one of the plurality of bends most adjacent to the central axis of the impeller having an angle in a range between 90° and 110°.
 18. The impeller as claimed in claim 11, with one of the plurality of bends most adjacent to the central axis of the impeller having an angle in a range between 90° and 110°.
 19. The impeller as claimed in claim 10, with each of remaining bends of the plurality of bends other than the one most adjacent to the central axis of the impeller having an angle in a range between 30° and 150°.
 20. The impeller as claimed in claim 11, with each of remaining bends of the plurality of bends other than the one most adjacent to the central axis of the impeller having an angle in a range between 30° and 150°. 